No. of days.

8 children and 10 men complete a certain piece of work in 9 days.Each child takes twice the time taken by a man to finish the work.In how many days will 12 men finish the same work?
(A)8
(b)9
(c)12
(d)15

8 children and 10 men complete a certain piece of work in 9 days.Each child takes twice the time taken by a man to finish the work.In how many days will 12 men finish the same work?
(A)8
(b)9
(c)12
(d)15

Usually, you can find in how many days a child finishes the work, etc...

Here's how I'd do. Since each child takes twice the time than a man, we can consider that 2 children are worth 1 man.
Hence 8 children worth 4 men. And thus 14 men would complete the piece of work in 9 days.